1. Field of the Invention
This invention relates to a method for converting various kinds of hydrocarbons, including heavy hydrocarbons, as well as light hydrocarbons, into a gaseous mixture rich with hydrogen by a catalytic partial oxidation process.
2. Description of the Prior Art
Heretofore, internal heating-type thermal or catalytic cracking processes, external heating-type catalytic cracking processes, and other similar processes have been employed industrially for producing hydrogen-rich gaseous mixtures from hydrocarbons.
In general, the known partial oxidation processes include two types, namely, (1) the non-catalytic process (thermal cracking process) in which no catalyst is used and (2) the catalytic process (catalytic cracking process) in which a catalyst is used. The present invention belongs to the latter type.
In the case of the non-catalytic partial oxidation process, either light or heavy hydrocarbons can be used as the starting material for the reaction, but according to this process, the hydrocarbons are thermally cracked at a high temperature of over 1,300.degree.C. using a large amount of oxygen, so that means for producing oxygen and a power source for operating such means are essential.
On the other hand, in the case of the catalytic partial oxidation process, usually only the light fractions from such substances as natural gas, ethane, propane, butane, straight-run naphtha or the like can be used as the starting material hydrocarbons. Use of heavy hydrocarbons such as kerosene, gas oil, crude oil, etc., has been considered unfeasible because carbon precipitation inevitably occurs during the reaction using such heavy hydrocarbons. Further, since a nickel catalyst is used as the reaction catalyst, the sulfur content of the hydrocarbons used as the starting material must be strictly limited to a level below that which would cause catalyst poisoning during the reaction. Hence, a high-grade preliminary desulfurization treatment of the starting material is essential.
In performing catalytic partial oxidation of heavy oils such as crude oil, there has been employed a regeneration-type gas producing method in which there are repeated in sequence (1) the step of burning the carbon precipitated on the catalyst with air so as to remove the precipitated carbon and also raising the temperature of the packed bed, and (2) the step of producing the hydrogen-rich gas. This method, however, involves unavoidable heavy losses and also involves difficulties in performing the operations under an elevated pressure.